The present invention relates to a portable power tool, in particular a drilling hammer and/or impact hammer.
A known rotary hammer (EP 1 157 788 A2) has a rotating sleeve referred to as a hammer tube that is connected with a tool holder in a rotation-proof manner. The hammer tube bearing arrangement in the housing is designed as a radial needle bearing located in the anterior region of the hammer tube that accommodates the tool holder, in a pot-shaped sleeve mounted on the housing. A driving gear-wheel designed as a spur gear and seated loosely on the hammer tube is connected with the hammer tube in a rotation-proof manner via a safety clutch and is driven by a pinion mounted on a driven shaft of a gearbox. The driving gear-wheel is also a clutch member of the safety clutch, the other clutch member being a driving ring. The driving ring is provided with teeth on its inner ring surface, these teeth meshing with outer teeth formed on a section of the hammer tube.
The two clutch members are held in engagement with each other by a coupling spring that is designed as a coil compression spring, is mounted on the hammer tube, and bears against a support shoulder formed on the hammer tube and against the driving gear-wheel. When a limit torque is exceeded—which occurs, e.g., when a tool becomes stuck in the work piece being machined—the two clutch members slip against the force of the coupling spring, and the driving gear-wheel can rotate relative to the hammer tube.